Much depends on the level and quality of the restoration. I'd see the car in the $15-30K range. "Restoration" is a very loosly defined word. To some it is some cosmetic improvements; to others it is a total disassembly and rebuild finished to concours standards. The '69-'70 Machs are more popular and will fetch higher market prices.
An additional thought: You should remember that this country is currently at war, if not formally, in action. Economic times were in a down cycle even before the WTC attack. Since then, there is a heightened sense of uncertainty (anthrax, smallpox, etc.) that is very pervasive. In such times, the collector car market goes in the dumper big time. I'm not saying that your car couldn't be worth more than I indicated but, if you want to do better, your timing must be right.
If you are restoring the car for your own use/satifaction it is different matter than restoring it to turn a profit. Making ANY profit, much less a large one, on a quality restoration is vertually impossible due to the hard costs involved. If you figure your labor into the equation, profit fades even farther from the picture. Ask anyone who has "done" are car.
I hear ya. I doubt there will be any profits in this resto but I never set out with that in mind. It is still interesting to know what they sell for in case i decide to do the deed. This car has been a complete back to baremetal resto. I am trying to keep it as original as possible and using correct parts for replacment though they are not always OEM. Living down here in NZ and restoring an American car puts a new twist on everything including the cost.